Interferons in Autoimmunity: From Loss of Tolerance to Chronic Inflammation.

Interferons (IFNs) are key cytokines at the intersection of innate and adaptive immunity. While their antiviral and antitumor roles are well recognized, emerging evidence implicates IFNs-particularly types I, II, and III-in the initiation and progression of autoimmune diseases (ADs). This review synthesizes current data on IFN biology, their immunoregulatory and pathogenic mechanisms, and their contributions to distinct AD phenotypes. We conducted a comprehensive review of peer-reviewed literature on IFNs and autoimmune diseases, focusing on publications indexed in PubMed and Scopus. Studies on molecular pathways, immune cell interactions, disease-specific IFN signatures, and clinical correlations were included. Data were extracted and thematically organized by IFN type, signaling pathway, and disease context, with emphasis on rheumatic and systemic autoimmune disorders. Across systemic lupus erythematosus, rheumatoid arthritis, Sjögren's syndrome, systemic sclerosis, idiopathic inflammatory myopathies, multiple sclerosis, type 1 diabetes, psoriasis, and inflammatory bowel diseases, IFNs were consistently associated with aberrant activation of pattern recognition receptors, sustained expression of interferon-stimulated genes (ISGs), and dysregulated T cell and B cell responses. Type I IFNs often preceded clinical onset, suggesting a triggering role, whereas type II and III IFNs modulated disease course and severity. Notably, IFNs exhibited dual immunostimulatory and immunosuppressive effects, contingent on tissue context, cytokine milieu, and disease stage. IFNs are central mediators in autoimmune pathogenesis, functioning as both initiators and amplifiers of chronic inflammation. Deciphering the context-dependent effects of IFN signaling may inform targeted therapeutic strategies and advance precision immunomodulation in autoimmune diseases.